Seats have a critical role in modem society. This is especially true of seating for wheelchairs. Especially for those users who must spend large amounts of time in a wheelchair, a seat (or “seat cushion” as it is commonly called) should achieve a number of objectives. First, it should maximize user function. This includes maximizing the user's ability to maneuver the chair and to engage in activities while in the chair. Second, the seat cushion should be comfortable for the user. Third, the seat cushion should be reliable and durable. Fourth, the seat cushion should be easy to clean and maintain. Finally, the seat cushion should be safe for the user.
Many aspects of wheelchair seat cushion design can simultaneously affect user comfort, function, and safety in the chair. For example, if a wheelchair user is not stable in the chair, the user likely will not be comfortable, will not have adequate function, and will not be safe.
When a user has decreased or absent sensation, a particular danger can be the formation of decubitus ulcers (commonly known as “pressure ulcers”). Decubitus ulcers are lesions that form on parts of the body that are in ongoing contact with objects such as beds or wheelchair seat cushions. The symptoms of decubitus ulcers range from skin redness (stage I) to “tunneling ulcers” with necrosis of the skin, fat, muscle and even bone (stage IV).
Wheelchair users can face a truly daunting (and even deadly) challenge in trying to prevent and manage decubitus ulcers. Decubitus ulcers can lead to hospitalization, plastic surgery, and even amputation. Once a patient has had an ulcer with skin scarring, the risk of future ulcers increases. Wheelchair users can face a repeating cycle of ulcer formation, hospitalization, surgery, and bed rest.
The repeated insult to the body, however, is only part of the affliction. Hospitalization and long-term bed rest can destroy families and social networks and severely hamper work and leisure. Costs incurred because of decubitus ulcers can be dramatic as well. In some cases, a single patient can incur ulcer-related medical costs that go well beyond one million dollars. Indirect costs such as lost productivity increase this monetary burden.
The general reason wheelchairs users face problems with decubitus ulcers is clear. Prolonged sitting in a wheelchair with no ability or limited ability to move the torso places tremendous cumulative loads on the body. The primary regions of the body affected are generally tissue near boney structures such as the sacrum, coccyx, ischial tuberosities (149a, 149b in FIGS. 2 and 3), and greater trochanters (147a, 147b in FIGS. 2 and 3). When “local factors” such as pressure, shear, heat, and moisture rise, the likelihood of ulcer formation increases.
Many developers of seat cushions have used various techniques to manage pressure to help prevent the formation of decubitus ulcers. Most developers in the past have focused on alleviating pressure. Typically, developers have tried to even out pressures across the entire area of the body in contact with the seat cushion. This might be described as “floatation.”
Broadly speaking, seat cushions fit in two categories. The first category includes custom seat cushions. The most sophisticated custom seat cushions are made by taking an impression of the intended user, making a mold from the impression, and using the mold to fabricate the seat cushion. The material used for the seat cushion is typically foam. In some cases, the seat cushion can have a monolithic foam component. In other cases, a less sophisticated seat cushion can be constructed from foam components pieced together.
The second category of seat cushions is non-customized, or “standardized,” cushions. These seat cushions can range from non-sophisticated seat cushions that have limited capacity to adjust to a user's anatomy to seat cushions that can be adjusted or adjust automatically in response to phenomena such as pressure on the seat cushion's weight bearing surface. The more sophisticated, adjustable seat cushions can include ones made of materials such as foams with special properties that adapt based on pressure or heat or ones with pneumatic systems that use air in compartments to create an adjustable weight bearing surface.
Other non-customized seat cushions use a liquid to achieve “floatation” or “equalization.” One such seat cushion is the “Jay® cushion.” It uses a high viscosity liquid positioned in cells or reservoirs underneath a user's boney prominences. There are also “dynamic” cushions. Dynamic cushions have cells that alternately fill changing supportive locations. One example is the “Aquila” seat cushion from Aquila Corporation of La Crosse, Wisconsin.
The prior art suffers from certain shortcomings or limitations, many of which are identified in the text below. The purpose of the device and method of the present disclosure is to overcome the shortcomings or limitations in the prior art.